The present invention relates to a nasal mask. Known nasal masks of which the applicant is aware have suffered from various disadvantages. For example, known nasal masks do not prevent leakage of gas such as air or oxygen from the mask efficiently, and do not distribute forces evenly on the face of the user. With known masks, an undesirably high tensile force has to be exerted by the straps or other mask retaining devices that hold the mask to the user""s head, and as a result excessive pressure tends to be exerted on the user""s face, causing breakdown of the skin, for example, on the bridge of the nose. Further, known masks interfere with use of eye glasses while wearing the mask, and may present the difficulty that a gas tube may become pinched or obstructed when the user lies on one side, for example when the user is sleeping.
The present invention provides a shell portion and an interface member for a nasal mask comprising a shell portion defining a hollow enclosure with a rearwardly facing opening defined by edge portions of the shell portion, and a resiliently deformable endless interface member engaging with and extending around said edge portion of the opening and adapted to form a seal between the shell portion and the user""s face, and wherein the shell portion and the interface member are at least generally symmetrical about a median plane, and said shell portion has two gas inlet orifices disposed one on each side of the median plane. With this arrangement, the mask may be supplied with gas through two relatively small diameter flexible tubes coupled to the orifices, respectively. The small diameter tubes exert only relatively small tensile forces away from the user""s face, and therefore only relatively small forces need to be exerted by retaining straps to retain the mask, and as a result, excessive application of force to the user""s face and problems such as breakdown of skin on the bridge of the nose can be avoided. Further, the smaller tubes can be easily oriented in any desired position relative to the mask. For example, they may be positioned downwardly below the mask to facilitate wearing of eye glasses, or may be positioned centrally of the top of the user""s head so that they are not obstructed if the user lies on one side.
In a preferred form, the gas inlet orifices are positioned symmetrically with respect to the median plane, and the inner side of the shell adjacent each orifice is provided with an inwardly extending tubular portion for engaging deformable nasal pillows that may form a seal between each orifice and a nostril of the user.
In one aspect, the present invention provides a nasal pillow, for use in combination with a nasal mask, the nasal mask comprising a shell portion and a resiliently deformable endless interface member engaging with and extending around an edge portion of an opening of the shell portion and adapted to form a seal between the shell portion and the user""s face, the shell portion having two inlet orifices and tubular pillow engaging members formed integrally with the shell portion and defining a flow passage through the orifices, the nasal pillow including a resiliently deformable corrugated tubular member adapted to be received in the nostrils of a wearer of the mask and to connect with the pillow engaging member, said tubular member comprising a tapering tip, a plurality of relatively narrow intermediate portions and a plurality of relatively wide intermediate portions, and wherein the tip is inclined with respect to the longitudinal axis of the tubular member.
Preferably, the edge portions defining the rearwardly facing opening of the shell are re-entrant edge portions so that the pressures within the mask tend to provide a rearwardly directed component of force tending to resist movement of the mask away from the face of the user. This allows the force applied by the retaining devices to be still further decreased, so that the effects of pressure on the skin of the face of the user may be further alleviated.
In another aspect, the present invention provides a shell portion for a nasal mask, the shell portion defining a hollow enclosure with a rearwardly facing opening defined by edge portions of the shell portion, and wherein the shell portion is at least generally symmetrical about a median plane, and the shell portion having two gas inlet orifices disposed one on each side of the median plane, the shell portion further including an attachment mechanism formed integrally with each orifice of the shell portion; and a swivel inlet adapted to be connected to each attachment mechanism and defining a flow passage through the orifice, the swivel inlet comprising a hollow cylindrical inlet tube having an elbow portion, and wherein the swivel inlet is rotatable around the axis of the attachment mechanism.
Preferred embodiments of the present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings.